1. Field of the Invention
The present invention generally relates to the field of fiber optic cables, in particular the present invention is directed to a new and novel method and apparatus for supporting and packaging optical fibers.
2. Discussion of Related Art
Optical fibers are very small diameter glass strands which are capable of transmitting an optical signal over great distances, at very high speeds, and with relatively low signal loss as compared to standard wire or cable networks. Optical fibers are used in many areas of technology, and because of this development, there is a growing need to have fiber optic cable configurations which can provide adequate support for the optical fibers, and which are sized so that they can be effectively used in various environments.
An example of a common fiber optic cable cross-section can be seen in FIG. 1. At the center of the cable is a central strength member 1. The central strength member 1 can be made from a number of different materials, such as hard plastic, glass, or a glass reinforced composite and is used as a load bearing member for the cable, as well as for supporting the inner sides of buffer tubes 2 that are typically stranded around the central strength member in a helical path. Although FIG. 1 shows six buffer tubes 2, the quantity can increase or decrease depending on the particular application the cable is to be used for. Within each buffer tube 2 is a plurality of individual optical fibers 3. The optical fibers 3 can be configured in any number of ways. For example, within each buffer tube 2 there can be a stacked ribbon configuration (as shown in FIG. 1) where each ribbon has a plurality of individual fibers and there are a number of ribbons. Alternatively, the fibers 3 can be configured as bundles inside the buffer tube. The configuration will greatly depend on the use and application of the cable. Finally, the outer jacket 4 provides protection to the internal components of the cable, while aiding to keep all of the components together. The outer jacket 4 provides protection from the adverse physical elements that a cable can be exposed to during its use and installation.
Conventional optical fiber configurations, as shown in FIG. 1, use extruded thermoplastic materials for the outer jackets 4 and buffer tubes 2 to protect the fibers 3 and to create housings. Unfortunately, these materials contract too much at low temperatures causing deformation of the fibers. To minimize contraction, the diameter of the central strength member 1 can be increased or radial steel wires can be inserted in the jacket. Strength yarns 5 are also used to increase tensile strength. These additional elements increase the size of the cable and add to the overall cost. Thus, a high fiber count cable is needed that provides sufficient support for the optical fibers while not substantially increasing the cross-sectional size and weight of the cable.
The present invention is directed to eliminating the above problems associated with the use of various thermoplastics and multiple components, to form optical fiber configurations. Thus, the invention improves the quality of the optical fiber cable while reducing the cross-section size, number of components and weight.
The present invention addresses the above problems by providing an optical fiber configuration and method. The optical fiber configuration comprises fibers that are grouped by buffer tubes using a lightweight fabric-type composite tape material to serve as a strength member. The configuration is manufactured by first providing a plurality of optical fibers upon the composite tape material. Gel or foamy glue is placed on the tape and is used as a filler and an adhesive to secure the optical fibers to the tape. A buffer tube is then formed by rolling the composite tape or helically wrapping the tape around the fibers such that the tape takes on a tube shape and surrounds the fibers. Furthermore, multiple buffer tubes may be bundled together to form a stack. This is done by providing an additional piece of composite material having gel on one side, and placing the buffer tubes on the gel side of the composite tape material. The stack is then formed by rolling the tape to enclose the buffer tubes while excess gel serves to fill in gaps. Multiple stacks may then be stranded to form a larger cable that uses another piece of composite tape material along with an additional rolling process, similar to that described above. The individual stacks may be formed to have a triangular or trapezoidal shape for efficient packaging.
Thus, the present invention provides an optical cable configuration with improved quality while reducing the cross-section size, number of components and weight. The configuration employs innovative geometry and cost-effective materials for both dielectric and armored optical fiber cables. The tape provides a way of supporting and manipulating the optical fibers without extensive reliance on extruded plastic tubes or additional strength members, resulting in a reduced diameter. The fibers can be grouped into traditional buffer tubes or cell structures for easy identification. Additionally, with the increased number of fibers, a self-supporting effect is created that permits the fibers to carry an increased amount of external load, which further reduces excessive reliance on expensive and space-consuming strength members.